-
(Oscillating) non-exponential decays of unstable states
(2012)
- We discuss deviations from the exponential decay law which occur when going beyond the Breit- Wigner distribution for an unstable state. In particular, we concentrate on an oscillating behavior, remisiscent of the Rabi-oscillations, in the short-time region. We propose that these oscillations can explain the socalled GSI anomaly, which measured superimposed oscillations on top of the exponential law for hydrogen-like nuclides decaying via electron-capture. Moreover, we discuss the possibility that the deviations from the Breit-Wigner in the case of the GSI anomaly are (predominantely) caused by the interaction of the unstable state with the measurement apparatus. The consequences of this scenario, such as the non-observation of oscillations in an analogous experiment perfromed at Berkley, are investigated.
-
Decay widths of resonances and pion scattering lengths in a globally invariant sigma model with vector and axial-vector mesons
(2008)
- We calculate low-energymeson decay processes and pion-pion scattering lengths in a two-flavour linear sigma model with global chiral symmetry, exploring the scenario in which the scalar mesons f0(600) and a0(980) are assumed to be ¯qq states.
-
Brief report on 'Radiative Phi decays with derivative interactions'
(2008)
- We study the line shapes of radiative $\phi$-decays with a direct coupling of the $\phi$ meson to the $f_{0}(980)$ and $a_{0}(980)$ scalar mesons. The latter couple via derivative interactions to $\pi_0 \pi_0$ and $\pi_0 \eta$, respectively. Although the kaon-loop mechanism is usually regarded as the dominant mechanism in radiative $\phi$ decays, here we test a different possibility: we set the kaon-loop to zero and we fit the theoretical curves to the data by retaining only the direct coupling. Remarkably, satisfactory fits can be achieved, mainly due to the effects of derivative interactions of scalar with pseudoscalar mesons.
-
Zero temperature properties of mesons in a vector meson extended linear sigma model
(2011)
- A three flavor linear sigma model with vector and axial-vector mesons is discussed. Preliminary results concerning on the symmetry breaking pattern, the question of parameterization, as well as the resulting meson masses are presented.
-
Thermal ground state for pure SU(2) Yang-Mills thermodynamics
(2008)
- In this proceeding the emergence of a composite, adjoint-scalar field as an average over (trivial holonomy) calorons and anti-calorons is reviewed. This composite field acts as a background field to the dynamics of perturbative gluons, to which it is coupled via an effective, gauge invariant Lagrangian valid for temperatures above the deconfinement phase transition. Moreover a Higgs mechanism is induced by the composite field: two gluons acquire a quasi-particle thermal mass. On the phenomenological side the composite field acts as a bag pressure which shows a linear dependence on the temperature. As a result the linear rise with temperature of the trace anomaly is obtained and is compared to recent lattice studies.
